President Michael D Higgins has laid a wreath at the General Post Office to mark the Easter Rising.
The President was joined by Taoiseach Enda Kenny at the event outside the GPO on O'Connell Street, Dublin, the building that served as the headquarters of the 1916 rebels.
Members of the Irish Defence Forces personnel took part in the State ceremony.
The event began with the lowering of the Irish tricolour.
A prayer was read and a piper played a lament before the Proclamation of Independence was read by a Defence Forces officer.
On Easter Monday 1916, rebel leader Patrick Pearse stood outside the GPO and read out the proclamation to herald the start of the insurrection against British rule.
After the President laid the laurel wreath, a minute's silence was held and the Last Post played.
The official ceremony concluded with the raising of the tricolour, the playing of Amhrán na bhFiann and a fly-past by four planes from the Air Corps.
Domhnach Cásca pic.twitter.com/Ak2F20qQ2g— Áine Ní Bhreisleáin (@AineEibhlin) April 16, 2017
Earlier today, Heritage Minister Heather Humphreys and deputy UK ambassador to Ireland Neil Holland attended a series of commemorative events in Glasnevin Cemetery in Dublin.
The programme included the raising of the tricolour over the monument to celebrated poet Dora Sigerson and the laying of wreaths at the graves of Edward Hollywood, the man who delivered the first tricolour flag to Ireland from France, and Peadar Kearney, the composer of Amhrán na bhFiann.
Ms Humphreys said: "These moments of commemoration provide us with an opportunity to recognise the legacy of those who went before us and their enduring influence on the Ireland of today."
The great grandson of Peader Kearney, Dualta Ó Broin, sang the anthem at the event.